<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>粘性定位</title>
    <!-- 重点： position: sticky;
            top: 0;     -->
    <style>
         body {
            height: 3000px;
         }
         .nav {
            position: sticky;
            top: 0;
            width: 800px;
            height: 50px;
            background-color: pink;
            margin: 100px auto;
         }
    </style>
</head>
<body>
    <div class="nav">我是导航栏</div>
   
</body>
</html>